The subject of the invention is the use of certain mixed formals of alkylpolyglycol ethers as defoaming agents in washing with strongly alkaline cleaning agents and the strongly alkaline cleaning agents containing the mixed formals of alkylpolyglycol ether defoaming agents.
Industrial cleaning agents, particularly those that are used in automatic installations for the cleaning of rigid surfaces, such as metal, ceramic or glass, as well as especially for the cleaning of bottles, are expected to have a low foaming level combined with a strong cleaning power when employed in the washing process. The industrial cleaning agents of the mentioned kind usually are products that contain strongly alkaline substances, such as especially alkali metal hydroxides or also alkali metal silicates or alkali metal orthophosphates, singly or in admixture. Such products make high demands on the defoaming agents not only with respect to the defoaming action but also with respect to the storage stability in the respective solid products.
The use of adducts of ethylene oxide and propylene oxide with compounds, such as fatty alcohols, fatty acids, polyglycerol and ethylenediamines as defoaming agents, is well known in solid as well as in liquid products for industrial cleaning.
In addition, British Pat. No. 1,488,108 discloses the use of nonionic polyglycol ether mixed formal derivatives with alcohols in alkaline reacting industrial cleansers as defoaming agents. However, it has been found that the storage stability of these polyglycol ether derivatives is not always adequate when they are included and processed into solid cleaning agents with a very high content of alkali, particularly 50% or more caustic alkali. Also desirable in the defoaming agents are a good biodegradability and stability in alkaline solutions so that they do not lose their effectiveness under sustained high temperatures during the cleaning process.